I am using an off canvas menu, which works great, but if certain menu entries are opened in an WebKit based browser (I can only test with iPadOS and iOS), the menu overflows to the right. You can see how the close button moves to the right. That doesnt happen on other devices, so I think it is some browser specific CSS issue, but I am not able to find out what the issue is.
i only notice it on smaller devices where there isn’t room for this link text: Reform des Psychotherapeutengesetzes
You can try adding word-wrap to the menu items:
#generate-slideout-menu .main-nav .sub-menu a {
word-wrap: anywhere;
}